1. Field of the Invention
The present invention relates to a method and a device for removing dust from areas with high dust loading.
2. Description of the Related Art
Areas with high dust loading can be found, for example, in blast jet chambers. Government regulations do not permit dust produced by jet blasting of workpieces which consists, for example, of removed rust, scales, paint coverings or abrasives, to enter the environment in the produced concentration and create an environmental hazard. For this reason, the aerosols generated in the blast jet chambers are treated as spent air and drawn off. By employing suitable methods, the spent air is subsequently separated from the solid constituents and dust, respectively, and exhausted to the surroundings, containing only a small residual dust fraction. The air volume to be treated depends on the number of the air changes necessary for providing sufficient visibility in the jet chamber. Accordingly, the number of the air changes is very high in comparison with the number of air changes required for controlling the air quality in conventional office and work areas.
Importantly, the pressure in blast jet chambers should always be slightly lower than the ambient pressure to prevent dust from uncontrollably escaping into the surroundings through leaks in the chamber. The slightly lower pressure guarantees that an air currents eaters the chamber from the outside at all times.
Air filters in the form of, for example, cartridge filters are suitable to separate the air and the dust particles and to attain a small residual dust fraction of approximately 1 mg/m.sup.3. The cartridge filters have the characteristic feature that the pressure drop increases with increasing filtration efficiency.
The energy consumption for cleaning the air is therefore determined by the pressure drop across the filter and the air flow through the filter. The energy consumption can become very high if the desired high separation efficiency requires a large pressure drop and the large exhaust air volume to be cleaned requires a large number of air changes.
A conventional method and device for removing fine dust particles is described, for example, in DE 43 00 830 C2. An essential feature is a here that the volume of fresh air is essentially equal to the air volume which is drawn off with the exhaust air and subsequently filtered by a fine filter.